If I want coffee, I want it now; I don't want to wait 15 mins. Also, if I am in my own office, I probably will have better quality coffee available than the one that can be delivered by a chain (Nespresso, AeroPress with freshly ground beans, etc.)
Then you're not the market because you wouldn't go to Starbucks anyway. For Starbucks customers in the Empire State Building, it's going to take 15 minutes to ride the elevator and stand in line.
Or they're delivering drip coffee which will have even less demand and cost less.